Battery management system

ABSTRACT

A method and apparatus are disclosed for a Battery Management System (BMS) for the controlling of the charging and discharging of a plurality of battery cells (12). Each battery cell has an associated plurality of control circuits (32, 36) which monitor and control the charging of individual battery cells. These units are controlled by a central microcontroller (14) which shunts current around the battery cell if fully charged and stops discharge if a battery cell is fully discharged in order to prevent damage to the other cells.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of co-pending U.S. patent applicationSer. No. 16/551,449, filed on Aug. 26, 2019, which is a continuation ofU.S. patent application Ser. No. 13/735,946, filed on Jan. 7, 2013, nowU.S. Pat. No. 10,396,570, which is a continuation of U.S. patentapplication Ser. No. 12/514,058, filed on Nov. 13, 2009, now U.S. Pat.No. 8,350,529, which is a national phase filing, under 35 U.S.C. §371(c), of International Application No. PCT/DK2007/000492, filed Nov.12, 2007, claiming priority from European Patent Application No.06388061.1, filed Nov. 10, 2006. The disclosures of the InternationalApplication and the European Application from which this applicationclaims priority are incorporated herein by reference in their entirety.

TECHNICAL FIELD

The present invention relates to systems and methods for controllingcharging and discharging battery cells such as lithium ion cells.

BACKGROUND OF THE INVENTION

The introduction of rechargeable lithium ion batteries opens newpossibilities of performances. Lithium technologies offer severaladvantages where maximum operating time and battery cycles life isrequired over wide temperature range, coupled with compact size andminimum weight. This technology needs strict charge and dischargecriteria. Protection and detection against abusive conditions is here ademand. A BMS (Battery Management System) is to be developed in order tofulfil these demands.

SUMMARY OF THE INVENTION

On the above background it is an object of the present invention toprovide a battery management system (BMS) that ensures optimal chargeand discharge conditions for each of the individual lithium cells andprotects the lithium cells from any abusive conditions such as overloadand/or short circuit.

These and other objects and advantages are according to the inventionattained by a battery management system (BMS) for the controlling andmonitoring of a plurality of lithium ion cells or similar battery cellsincluding lithium molybdenum, nickel, cadmium and PB cells, the BMSincluding a central controlling microcontroller and a plurality ofcontrol circuits connected with a respective battery cell and serving toindividually monitoring the charging of the individual respectivebattery cell and at the time of reaching a maximum charging stateestablishing a shunt across the individual battery cell for allowing acontinued charging of the remaining battery cells and at the same timecommunicating to the central controlling microcontroller a messagerepresenting that the maximum charging state has been reached andserving during discharging of the battery to monitor the state of theindividual respective battery cell and to inform the central controllingmicrocontroller in case a minimum charging state has been reached forcausing the central controlling microcontroller to disconnect thebattery from the load in order to prevent excessive discharging of theindividual battery cells.

According to a specific embodiment of the invention said BMS comprisestemperature sensors for continuous monitoring of the temperature in thedevice, means to shut down the charging/discharging in case ofoverload/short circuit, current monitoring by means of a shunt resistor,fuse protection of the device in case of overload/short circuit, a powersupply for the control unit and a fuel gauge.

The above and other objects and advantages are furthermore according tothe invention attained by a method for controlling and monitoring aplurality of lithium ion cells or similar battery cells includinglithium molybdenum, nickel, cadmium and PB cells, the method comprising:

during charging of said cells:

adjusting the voltage/current with respect to the cell condition toachieve optimum charge performance and bypassing one or more individualcells for allowing continuous charging of the remaining cells when saidone or more individual cells has reached the top voltage;

during discharging of said cells:

the voltage of each individual cell is monitored until a minimum valuehas been reached in one or more individual cells at which time all thecells are shut down to prevent the lithium ion cell having reached theminimum voltage level to be ruined by continuous discharging;

thereby ensuring the highest performance of the battery maximum safetyduring charging and discharging.

The present invention furthermore relates to a battery management system(BMS) of a modular design, where the system can be adapted to differentnumbers and physical placements of rechargeable cells. In a modularsystem according to the invention circuits/functions common to all cellsare thus provided centrally, for instance on a single PCB or otherwise,whereas individual cells can be provided with corresponding controlsystems comprising cell balancing means and/or slave sensor means, theindividual control systems being either of a type common for all cellsin the system or individually adapted to each individual cell. Thecontrol systems at the individual cells can communicate with the centralcircuits of the system by wired connections, e.g. an analogue connectionor a digital communication bus according to the specific implementationof the system. It would, however, alternatively be possible to providecommunication between the individual cell control systems and thecentral parts of the system by wireless communication means, henceincreasing the flexibility of the entire set-up even further.

In the following detailed description of the invention the concepts ofthe invention will be illustrated by reference to two specificembodiments of the invention, but it is understood that the scope of theinvention is not limited to those embodiments. Even though theembodiments shown and described in the detailed description of theinvention relate to a specific number of cells and to specific voltagesover each individual cell and over the entire batter the invention isnot limited to these specific numerical values. In fact any number ofindividual cells may be included in the system and method of theinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be better understood with reference to thefollowing detailed description of embodiments of the invention taken inconjunction with the figures, where:

FIG. 1 shows a schematic block diagram of a first embodiment of a BMS(Battery Management System) according to the present invention;

FIG. 2 shows a diagrammatic view illustrating the charging of a 14 celllithium ion battery when using the BMS of FIG. 1;

FIG. 3 shows a diagrammatic view similar to the view of FIG. 2 of thedischarging of the 14 cell lithium ion battery when using the BMS ofFIG. 1;

FIG. 4 shows a schematic block diagram of a second embodiment of a BMS(Battery Management System) according to the present invention;

FIGS. 5A and 5B show a schematic view of a battery switch from thesecond embodiment of a BMS (Battery Management System) according to thepresent invention;

FIG. 6 shows a schematic view of a power supply from the secondembodiment of a BMS (Battery Management System) according to the presentinvention;

FIG. 7 shows a schematic diagram of a start-up of the power supply fromFIG. 6 of the second embodiment of a BMS (Battery Management System)according to the present invention;

FIGS. 8A, 8B, 8C, 8D, and 8E show schematic views, respectively, of asupply part for the communication bus, an internal temperature sensor,an external temperature sensor and an output fuel gauge from the secondembodiment of a BMS (Battery Management System) according to the presentinvention;

FIG. 9 shows a schematic view of a synchronizing and control unit fromthe second embodiment of a BMS (Battery Management System) according tothe present invention;

FIGS. 10A and 10B show, respectively, schematic views of a cellbalancing module and a cell voltage measurement module from the secondembodiment of a BMS (Battery Management System) according to the presentinvention;

FIGS. 11A, 11B, and 11C show a schematic view of a single wire bus fromthe second embodiment of a BMS (Battery Management System) according tothe present invention;

FIG. 12 shows a schematic view of a cell to master the microcontrollercommunication bus; and

FIG. 13 shows a schematic view of a battery management system mainconnectors layout.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1 there is shown a schematic block diagram of a firstembodiment of the battery management system or BMS according to theinvention, which is shown connected to a plurality of lithium ion cells,in the embodiment shown in FIG. 1 a total of 15 lithium ion cells. Oneof the lithium ion cells is designated the reference numeral 12 and theBMS is in its entirety designated the reference numeral 10.

The BMS centrally includes a master microcontroller performing theoverall sensing and control of the BMS, which central microcontroller isdesignated the reference numeral 14. The microcontroller 14 isconnectable to external equipment such as an external PC through aninterface connector 16. The BMS is connected to a common groundconnector or terminal 18 and is connected to a charge input connector orterminal 20 through a charge control MOSFET 22 serving to separate thecharge input connector from a battery output connector 24 constitutingthe positive output terminal of the battery system relative to thecommon ground connector or terminal 18.

The series configuration of the 15 lithium ion cells defines a positiveterminal which is connected to the junction between the battery outputterminal or connector 24 and the battery voltage sensor terminal of thecharge control MOSFET 22. The negative terminal of the seriesconfiguration of the 15 lithium ion cells is connected through a seriesconfiguration of a discharge control MOSFET 26 and low ohm resistor tothe common ground connector or terminal 18. The voltage across the lowohm resistor 28 is sensed by current amplifier delivering an outputvoltage in response to an excessive current passing through the low ohmresistor 28 for informing the central master microcontroller 14 of theoccurrence of an excessive current load through the series configurationof the 15 lithium ion cells. The discharge controlling MOSFET 26 iscontrolled by the central master microcontroller 14 and is used for ashut down of the supply of current from the lithium ion cells as will bedescribed below.

As a particular feature of the BMS according to the present inventioneach lithium ion cell is connected to a separate monitoring andcontrolling circuit including for each lithium ion cell a cell balancingcircuit 32, a temperature sensor 34 and a communication or sensing slavecircuit 36 establishing communication from the cell balancing circuit 32and the temperature sensor to and from the central mastermicrocontroller 14. The cell balancing circuit 32 basically serves tomonitor the voltage across the lithium ion cell during charging and incase the lithium ion cell connected to the cell balancing circuit inquestion has reached the top voltage and the master microcontroller 14is still controlling the BMS into continuous charging of the remaininglithium ion cells, the cell balancing circuit 32 shunts the lithium ioncell for allowing the continuous charging of the remaining lithium ioncells.

The temperature sensor 34 serves to monitor if an excessive temperatureis reached in the lithium ion cell and/or in the cell balancing andsensing slave circuits 32 and 36, respectively, and the sensing slavecircuit 36 serves during discharging of the lithium ion cell to monitorthe discharging of the lithium ion cell to a minimum at which time thesensing slave circuit 36 informs the master microcontroller 14 of theoccurrence of a complete discharging of one of the cells causing themaster microcontroller 14 to shut down the whole circuitry in order toprevent the lithium ion cell having reached the minimum voltage level tobe ruined by continuous discharging of the lithium ion cell.

Referring to FIG. 2 there is shown a diagram illustrating theadvantageous charging of a total of 14 cells by the use of the BMS asshown in FIG. 1, however, modified into communicating with 14 lithiumion cells rather than 15 lithium ion cells as illustrated in FIG. 1.From FIG. 2 it is evident that the individual lithium ion cells arecharged simultaneously to the same maximum level of approximately 4.2V.

Referring to FIG. 3 there is shown a diagram illustrating theadvantageous discharging and control of a total of 14 cells by the useof the BMS as shown in FIG. 1, however, modified into communicating with14 lithium ion cells rather than 15 lithium ion cells as illustrated inFIG. 1. From FIG. 2 it is evident that of each of the individual cellsis monitored and the battery as a whole is allowed to be shut down atthe time a single lithium ion cell reaches the minimum voltage level of2.8V.

Referring to FIG. 4 there is shown a schematic block diagram of a secondembodiment of the battery management system or BMS according to theinvention, which is shown connected to a plurality of lithium ion cells,in the embodiment shown in FIG. 4 a total of 15 lithium ion cells. Oneof the lithium ion cells is designated the reference numeral 12 and theBMS is in its entirety designated the reference numeral 10.

The BMS centrally includes a master microcontroller 14 performing theoverall sensing and control of the BMS. The master microcontroller 14 isconnectable to external equipment such as an external PC through anexternal device bus 16.

The BMS is connected to a common battery connector or terminal 24 whichis connected to the series configuration of the 15 lithium ion cells 12and defines a positive terminal. The negative terminal of the seriesconfiguration of the 15 lithium ion cells is connected through a low ohmshunt resistor 28. The voltage across the low ohm shunt resistor 28 issensed by current amplifier 44 delivering an output voltage in responseto an excessive current passing through the low ohm shunt resistor 28during charging or during discharging for informing the central mastermicrocontroller 14 of the occurrence of an excessive current loadthrough the series configuration of the 15 lithium ion cells. In case ofa short circuit/overload the threshold of charging currents ordischarging currents is reached and the central master microcontrollershuts down the charging/discharging process.

The low ohm shunt resistor 28 is further connected to a junction betweenthe load enable MOSFET 26 and the charge enable MOSFET 22 serving toseparate the load discharging out ground terminal 18 and the charging inground terminal 20. The load enable MOSFET 26 and the charge enableMOSFET 22 are controlled by the central master microcontroller 14 and isused to connect the lithium ion cells to the load in case of dischargingand to the charger in case of charging and to shut down the supply ofcurrent in case of short circuit/overload as will be described below.

As a particular feature of the BMS according to the present inventioneach lithium ion cell is connected to a separate monitoring andcontrolling circuit including for each lithium ion cell a cell balancingcircuit 32 and a communication and sensing slave circuit 36 establishingcommunication from the cell balancing circuit 32 to and from the centralmaster microcontroller 14. The sensing circuit 36 serves to monitor thevoltage across the lithium ion cell during charging and in case thelithium ion cell connected to the cell balancing circuit in question hasreached the top voltage and the master microcontroller 14 is stillcontrolling the BMS into continuous charging of the remaining lithiumion cells, the cell balancing circuit 32 shunts the lithium ion cell inquestion which has reached the top voltage for allowing the continuouscharging of the remaining lithium ion cells.

The shunting is done by the cell balancing circuit 32 by shorting thepositive and the negative pole of the cell through a power resistor anda fast switching transistor. PWM modulation is in an embodiment of theinvention done to ensure an adjustable current through the resistor.

The sensing slave circuit 36 serves during discharging of the lithiumion cell to monitor the discharging of the lithium ion cell to a minimumat which time the sensing slave circuit 36 informs the mastermicrocontroller 14 of the occurrence of a complete discharging of one ofthe cells causing the master microcontroller 14 to shut down the wholecircuitry in order to prevent the lithium ion cell having reached theminimum voltage level to be ruined by continuous discharging of thelithium ion cell.

A power supply fed from the battery is used to supply the electronics ofthe BMS with DC voltage. Switching transistors connected in half bridgeconfiguration and filtered by a low pass filter and further regulated byvoltage regulators provide the necessary voltages for the controllingelectronics.

An internal temperature sensor 34 serves to monitor and report to themaster microcontroller 14 the temperature in the master microcontroller14 and in case an excessive temperature is reached the mastermicrocontroller 14 the charging/discharging will shut down. A batterytemperature sensor 40 serves to monitor and report to the mastermicrocontroller the temperature in the lithium ion cell and/or in thecell balancing and sensing slave circuits 32 and 36, respectively. If anexcessive temperature is reached in the lithium ion cell and/or in thecell balancing and sensing slave circuits 32 and 36 the mastermicrocontroller will shut down the charging/discharging process.

A cell communication bus 42 is used for the communication between themaster microcontroller and a slave microcontroller provided in eachindividual slave circuit. The bus is separated from the mastermicrocontroller by an isolation stage and (de)coupling 38. The bus isalso used for the fuel gauge where the remaining capacity of the batteryis reported.

Referring to FIGS. 5A and 5B there is shown a detailed schematicdescription of a discharge enable and charge enable switch and thecurrent sensing shunt resistor. The BMS contains two parallel CMOSswitches which serve to separate the charging input ground connectorfrom the battery output ground connector. Each switch is created by aparallel connection of MOSFETs where MOSFET number D1 up to D20 are usedfor connecting the load during discharging and MOSFET number D52, D55,D68, D64, D65, D67 are used for connecting the charger during charging.

The load is switched to the battery with ‘HIGH’ level of BATTERY_SWsignal, thereby connecting the positive voltage derived from +15Vthrough Q2 and Q1 transistors. The charger is switched to the batterywith ‘HIGH’ level of CHARGER_SW signal, thereby connecting the +15Vthrough Q29 and Q28 transistors.

The hardware shutdown is activated by reaching the threshold levelderived from the shunt resistor in the case of overload/short circuit.The analogue value of the charge current is derived from the U2Binverter output CHARGE. The analogue value of the load current is donein two ranges where the lower current range is read out from output ofU4A and the higher range is read out from the output of U2A opamp wherethe margings of the lower and higher current interval will varydepending on the application and will be set up by gain determiningresistors of non-inverting amplifiers R8, R7, R35. The Q30 transistorenables or disables the supply for charge current sensing opamp forpower saving reasons.

In case the melting fuse F2 blows due to short circuit through D61 andD71 MOSFETs to prevent the deep discharging of the battery the “Fuseblow” shutdown is initiated by 2 signals in logical AND functionprovided by Q16 and Q17 to avoid random triggering of “Fuse blown”shutdown. In case of hardware shut down due to a high current level a‘HIGH’ level of the SHUT DOWN signal on the Q4 transistor will result inopening of the Q4 transistor which remains open by positive voltagefeedback through R24 resistor. The shutdown can be terminated only bychanging the level of the SHUTDOWN_RST signal thereby cutting of the Q5transistor and disconnecting the positive voltage feedback provided bythe R24 resistor.

Referring to FIG. 6 there is shown a detailed schematic description of apower supply for the control module which is created by D41 and D40switching transistors connected in halfbridge configuration and drivenby U22 halfbridge driver where feedback from the battery voltage isapplied through U4B opamp connected in voltage follower configuration inthe function as a buffer. The DC output from the control module iscreated by filtering the pulsing DC voltage from the switchingtransistors with LC filter L1 and C64 and regulate the voltage byvoltage regulators U24 (15V output+15V_ON) and U23 (5V output+5V_ON) and+9V by using D48 Zener diode and +5V by U20 regulator where the 5Voutput is supplied directly from the battery for supplying the mainmicrocontroller in the sleep mode. The +5V output is disabled by Q25which opens when the PWM (Pulse-Width Modulation) of the halfbridge isactive.

Referring to FIG. 7 there is a diagram view of the start-up sequence ofthe power supply where AUX_START signal ‘HIGH’ after power-up of themaster microcontroller (1) provides temporary power supply for thehalfbridge. After approx. 100 ms the DC voltage is fully developedresulting in ramp up of the +5V_ON voltage (2) and after additionally100 ms the temporary power supply is terminated (3).

Referring to FIG. 8A there is shown a detailed schematic description ofa supply part for the communication from the master microcontroller tothe slave microcontroller communication bus where signal from the mastermicrocontroller to the slave microcontroller TX_CELL is amplified by Q10transistor.

Referring to FIG. 8B there is shown a detailed schematic description ofa supply part for the communication from the slave microcontrollercommunication bus to the master microcontroller where the signal fromthe slave microcontroller to the master microcontroller is supplied by a+5V_ON signal and the current is limited by R194 resistor when RX_CELLis switched to ground to provide the “LOW” signal level.

Referring to FIG. 8C there is shown a detailed schematic description ofan internal temperature sensor where the internal temperature is sensedby R45 thermistor.

Referring to FIG. 8D there is shown a detailed schematic description ofan external temperature sensor where the external or battery temperaturesensing is provided by transient voltage suppressor diodes, voltagelevel adjusting resistors, filtering capacitors and external NTCthermistor.

Referring to FIG. 8E there is shown a detailed schematic description ofan analogue output for a fuel gauge where the voltage level is adjustedby a R44 resistor. The fuel gauge use the PWM output (V_OUT) where theduty cycle of the output can be used for deriving the remaining capacityof the battery alternatively the PWM output (V_OUT) can be used to carrybinary information for a digital fuel gauge. The fuel gauge is countingall currents going in an out of the battery. A two stage amplifier Q11,Q13, Q12, Q14 is used to improve current carrying capability of thePWM_output. The stages in the two stage amplifier are filtered byparallel RC network and separated by a ISO1 optocoupler from the mastermicrocontroller.

Referring to FIG. 9 there is shown a synchronizing and control unit forthe slave microcontroller for controlling shut down, enabling chargingor discharging and sensing circuit. Each slave have their own addressfor the master to recognize them and each slave individually receivessynchronise pulse and values for cell balancing from the master andsends voltage measurements and status information to the master. Thesensing circuit consists of current sensing of the discharge current(DISCHARGE_HIGH, DISCHARGE_LOW), sensing of the charging current(CHARGE), sensing of the internal temperature (TEMPSNS_INT), sensing ofthe external temperature (TEMPSNS_EXT) and sensing of the batteryvoltage (BATTERY_VOLTAGE). The power supply of the control module issupported at the startup by a START_AUX signal and the switching of thehalfbridge is regulated by a PWM_AUX signal and the feedback from theoutput+5V_ON when the halfbridge is ready to supply its driver from itsown output. The 5V_uP can disable the current sensing opamps therebyreducing the power consumption in the sleep mode. The CMOS switch forenabling charging is controlled by CHARGE_SW signal and the CMOS switchfor enabling discharging is controlled by BATTERY_SW signal. The ‘HIGH’SHUT_DOWN signal will disconnect the +15V from the gates therebysecuring open status of the MOSFETs and the almost immediately following‘HIGH’ level of the TURN_OFF signal secures the fast discharging of thegates through 12 ohm resistor. The microcontroller provide a shut downstatus cancelling by a SHUT_DOWN signal at ‘LOW’ level for at shortperiod of time and the driving signals for OUT_1 and OUT_2: OUT_1_DRIVEand OUT_2_DRIVE. The ‘HIGH’ level of WAKE_UP signal provides a lowsignal on the pin 1 of the Microcontroller through grounding thecollector of Q8 thereby activating the microcontroller from power save(standby) mode. The cell communication is provided by TX_CELL (transferto cell) signal and RX_CELL (receiving from cell) signal thereby thecharge can be regulated by the BMS by transferring information to thecell by using TX_CELL and receiving information from the cell by usingthe RX_CELL signal and further diagnostics of the BMS can be made usingthe appropriate software.

Referring to FIG. 10A there is shown a cell balancing module where thecharging of each individual cell is controlled by its own voltage spikeprotected microcontroller. Cell balancing is provided by shorting thepositive and negative pole of the cell through a power resistor and afast switching transistor. PWM is used to ensure adjustable currentthrough the resistor. The slave receives a voltage from the master,calculated the difference between the received value and computes theduty cycle for the cell balancing PWM. If the cell voltage is lower thanthe received voltage from the master the PWM is set to zero.

Referring to FIG. 10B there is shown a cell voltage measurement modulewhere measurement is done by a voltage divider made of parallel 1 k ohmresistors where the analogue value is connected to pin 3 of themicrocontroller. The cell balancing is stopped while measuring voltageto avoid a voltage drop in cables. The measurement is transmitted to themaster microcontroller. In the sleep mode the voltage sensing isdisabled by turning off the NPN transistor resulting in the PNPtransistor being cut off as well.

Referring to FIG. 11A there is shown a single wire bus for communicatingthe TX and RX signals to a single wire DATA including galvanic isolationfrom the source and amplifying by D64 transistor.

Referring to FIG. 11B there is shown a power stage of the outputOUTPUT_1

Referring to FIG. 11C there is shown a protection circuitry of thethermistor monitoring the battery and/or in the cell balancing andsensing and control circuits.

Referring to FIG. 12 there is shown a cell to master microcontrollercommunication bus for decoupling the TX_CELL signal to RX1 up to RX15signals and coupling of the TX1 up to TX15 to RX_CELL signal.

A detailed description of an embodiment of the invention is given withreference to the following annexes, where:

ANNEX A contains a technical description;

ANNEX B contains a software description; and

ANNEX C contains detailed circuit diagrams of portions of the system.

Annex A System Specification Battery Voltage Amount of cells 15 Cellvoltage 2.8 V-4.2 V/cell Minimum voltage 42 VDC Maximum voltage 63 VDCDC Current Continuous discharge current 150 A Handling Peak dischargecurrent (<8 s) 250 A Max. charge current handling 35 A Peak chargecurrent (<1 s) 50 A Measurements/ Single cell voltage <1% AccuracyBattery voltage <1% Δ temperature resolution <0.25° C. Temperature +/−3°C. Cell Balancing Maximum bypass current 1 A Adjustable from 0 A BMSPower Standby consumption <250 μA Consumption Active consumption <50 mAOverload Discharge >200 A Software shutdown Resting period 10 s, 3attempts in a row to restart BMS Custom overload behavior TBD ShortCircuit Battery short circuit activation Hardware shutdown Restingperiod 10 s, 3 attempts in a row to restart BMS Custom Short circuitbehavior TBD Fuse MEGA FUSE from Littel fuse 175 A High Heat sinkPassive Temperature Protection Termination due overload Over-voltageBattery disconnection response 20 ms time when overvoltage appearsSingle cell disconnection in 1 s the case of overvoltage Under-voltageDevice shut down TBD Operating Minimum ambient temperature −20° C.Conditions Maximum ambient temperature +50° C. Maximum operating +105°C. temperature

Mainboard Description

The BMS module can be in principle described as a high current capacityCMOS switch featured by emergency shut down in the case of short-circuitor overload of the battery. This switch provides connection of thecharger to the battery in the case of charging and to the load (motor)during normal operation.

Battery switch for charger and load controlled by microcontrollerfeatured by hardware shut down in the case of overload or short circuit;current sensing

Power supply for the control module

Supply part for the cell communication bus and analogue output reservedfor fuel gauge

Master microcontroller

See FIGS. 5A and 5B Function:

Battery switch for charger and load controlled by microcontrollerfeatured by hardware shut down in the case of overload or short circuit;current sensing. Additionally “fuse blow” shutdown is introduced toprevent the deep discharging of the battery in the case of short circuitof switching MOSFETS.

Description:

The BMS contains two parallel CMOS for connecting the battery to thecharger or to the load. Each switch is created by a parallel connectionof MOSFETs: Transistors D1 up to D20 for the load connection and theswitch for charger connection is created by a parallel combination ofD52, D55, D68, D64, D65, D67 transistors.

In the normal mode the load is switch to battery with ‘HIGH’ level ofBATTERY_SW signal. This connects the positive voltage derived from +15Vthrough Q2 and Q1 transistors. The connection of the charger is enabledby Q29 through Q28 transistors with ‘HIGH’ CHARGER_SW signal.

The hardware shutdown is activated by reaching the threshold level ofcurrents in the case of overload/short circuit. The current level isderived from the shunt resistor R1, the analogue value of the chargecurrent is derived from the U2B inverter output—CHARGE. The readout ofthe load current is done in two ranges: for the lower current range isread out from output of U4A and the higher range from the output of U2Aopamp. The margins of lower and higher current interval will be variousdepending on the concrete project and will be set up by a gaindetermining resistors of a non-inverting amplifiers R8, R7, R35. The Q30transistor enables or disables the supply for charge current sensingopamp for power saving reasons.

The hardware shut down initiated by a high current level will result the‘HIGH’ level of the SHUT_DOWN signal on the Q4 transistor resulting theopening the Q4 transistor, which remains open through positive voltagefeedback through R24 resistor (note that the level of the SHUTDOWN_RSTsignal is ‘HIGH’ during normal operation.

Positive voltage of SHUT DOWN opening Q6 closes Q2 resulting the cut offof the Q1 transistor which disconnects the +15V source before connectingthe gates of the switches to ground to prevent the short circuit of+15V_ON to the ground which could appear when gates of transistors aregrounded.

The shutdown can be terminated only by changing the level of theSHUTDOWN_RST signal cutting off the Q5 transistor and disconnecting thepositive voltage feedback provided by R24 resistor.

The shut down initiated by a microcontroller is done by setting thelevel of TURN_OFF to ‘HIGH’ level (software shutdown).

The “fuse blow” shutdown is providing by connecting the positive andnegative poles of the battery resulting short-circuit through D61 andD71 MOSFETs. The short circuit current will blow the charger fuse F2.The “fuse blow” shutdown is initiated by 2 signals in logical ANDfunction (provided by Q16 and Q17 circuitry) to avoid random triggeringof this type of shutdown. The activating of the charger is indicated toprocessor by “HIGH” CHARGER_ACTIVE signal.

See FIG. 6 Function:

Power supply of the control module

Description:

The core of the power supply fed from battery and created by a D41 andD40 switching transistors connected in halfbridge configuration drivenby a U22 halfbrigde driver. Feedback from the supply (battery) voltageis applied through U4B opamp connected in voltage follower configurationin the function as a buffer.

The DC output is created by filtering the pulsing DC voltage withlowpass LC filter (parallel connection of L1 and C64). The regulatedvoltages are provided by voltage regulators U24 (15V output+15V_ON) andU23 (5V output+5V_ON); +9V by using D48 Zener diode and +5V by U20regulator. The +5V output is supplied directly from the battery and itis meant only for supplying the main microcontroller in the sleep mode.The +5 V output is disabled by Q25 transistor, which opens when the PWMof the halfbridge is active,

Firstly the AUX_START signal I ‘HIGH’ at the startup to ensure thesupply VCC voltage for the drive. After some time this signal is set to‘LOW’ and the VCC is derived from the +15V_ON voltage. The startup ofthe switching power supply of the control module can be described asshown on FIG. 1. After power up of the master microcontroller (1.) theprocessor set up the AUX_START signal to “HIGH” to provide the temporarysupply for the halfbridge driver. After a certain time (approx. 100 ms)the DC voltage is fully developed resulting the ramp up the +5V_ONvoltage (2.). To ensure the correct function of the power supply, thetemporary supply is hold on for additionally 100 ms and after this it isterminated (3.).

See FIG. 7 See FIGS. 8A, 8B, 8C, 8D, and 8E Function:

Supply part for the cell communication bus and analogue output reservedfor fuel gauge

Description:

The transfer signal from the microcontroller to cells TX_CELL isamplified by a Q10 transistor. The signal received from the slavemicrocontrollers by a master controller is supplied by a +5V_ON signaland the current is limited by a R194 when the RX_CELL is switched toground to provide the “LOW” signal level. The internal temperature issensed by a R45 thermistor and the voltage level for the controller isadjusted by a R44 resistor.

For the fuel gauge is reserved the PWM output (V_OUT), where the dutycycle of the output (i.e. the pulse width) can be equal to the remainingcapacity of the battery or it is also capable to carry binaryinformation for digital fuel gauge. The current carrying capacity of theoutput is improved by a two stage amplifier created by Q11,Q13 andQ12,Q14. The stages in cascade connections are filtered by a lowpassfilters created by a parallel RC networks. This output is also separatedby a ISO1 optocoupler from the master microcontroller.

The circuitry for the external temperature sensing is created by atransient voltage suppressor diodes, voltage level adjusting resistors,filtering capacitors and the external NTC thermistor.

See FIG. 9 Function:

Synchronizing and the control of the slave microcontrollers. Controllingof the shut down and enabling of the load and the charger.

Description:

Microcontroller can be programmed and reconfigured by a J32 connector.The signals for synchronizing and controlling can be divided tofollowing groups:

Sensing circuits

Control module power supply startup and regulation

CMOS switch control

Cell communication

Charger communication

Analogue/digital output

The sensing circuitry consists of current sensing of a load current(DISCHARGE_HIGH and DISCHARGE_LOW) and the charging current (CHARGE),sensing of the internal temperature (TEMPSNS_INT) and the temperature ofthe battery (TEMPSNS_EXT), sensing of the battery voltage(BATTERY_VOLTAGE).

The power supply of the control module is supported at the startup by aSTART_AUX signal and the switching of the halfbridge is regulated by aPWM_AUX signal and the feedback from the output+5V_ON to notify when thehalfbridge is ready to supply its driver from its own output. The +5V_uPcan disable the supplying the current sensing opamps thus reducing thepower consumption in the sleep mode.

The CMOS switch of the charger is switched by CHARGE_SW signal and theload switch is controlled by a level of a BATTERY_SW signal. In the caseof the shut down the positive voltage SHUT_DOWN will disconnect the +15Vvolts from the gates securing the open status of the MOSFETs and almostimmediately after that the ‘HIGH’ level of the TURN_OFF signal securesthe fast discharging of the gates through 12.OMEGA. resistor.

The cell communication is provided by a TX_CELL signal (transfer tocells) and RX_CELL (receiving from the cells).

During the charging the charge can be regulated by BMS transferringinformation to a charger using TX signal and receiving information fromthe charger—RX signal. These signals can be used for a diagnostic of theBMS with the proper software.

The microcontroller provide a shut down status cancelling by a SHUT_DOWNsignal at ‘LOW’ level for a short period of time and the driving signalsfor outputs OUT_1 and OUT_2: OUT_1_DRIVE and OUT_2_DRIVE.

The processor is activated from the power save (standby) mode by “HIGH”level of WAKE UP signal which will provide low signal on the pin 1 ofthe Microcontroller through grounding the collector of the Q8.

Control Module

The main function of the control module is the supervising the chargingof the separate cells of the battery and the overall charging bycontrolling of the charger.

See FIGS. 10A and 10B Function:

Cell balancing

Description:

Each separate cell of the battery is controlled by its own voltage spikeprotected microcontroller. The cell balancing is provided by shortingthe positive and negative pole of the cell through the power resistor.The bypassing is done by a PWM modulation to ensure the adjustablecurrent through the resistor. The cell is bypassed through fastswitching transistor. The cell voltage measurement is done by a voltagedivider made of parallel 1 k.OMEGA. resistors, where the analogue valueis connected to pin 3 of the slave microcontroller.

In the sleep mode the voltage sensing is disabled by turning off the NPNtransistor resulting the cut off the PNP transistor as well.

See 11A, 11B, and 11C Function:

Single wire bus for a charger communication and output interface.

Description:

Converting TX and RX signals to a single wire DATA featured galvanicisolation from the source and amplifying by D64 transistor. The controlmodule also includes power stage of the output OUTPUT_1. On controlboard there is an additional protection circuitry of the thermistorlocated on the mainboard.

See FIG. 12 Function:

Cell to microcontroller communication bus signal coupling/decouplingincluding galvanic isolation.

Description:

Decoupling the TX_CELL to RX1 up to RX15 signals and coupling of the TX1up to TX15 to RX_CELL signal.

Software Features Internal Functions: Analogue Measurements

Measurement of the battery voltage, current sensing, temperature sensingis described in the hardware part—refresh time: 10 msec

Power Management

To minimize the power consumption in the sleep mode some power savingfeatures are involved in the design:

Disconnecting the charger

Disabling the voltage measuring of the separate cells

Disable the continuous current sensing (sample monitoring 10 times persecond)

Disabling the power supply for the control circuitry except the mastermicrocontroller

Power Supply

Power supply start up voltage.¹ 27.78 V Power supply output voltage 20 VPower Supply Max PWM duty cycle 90% ¹Minimum overall voltage required tostart up the power supply

Functions: Charging

Charging max current (<1 sec)² 35 A Charging max current (<40 msec)³ 50A Charging shutdown resting time⁴ 10 sec Shutdowns in a row⁵ 3 Cellvoltage max⁶ 4.25 V Cell voltage max reset 4.15 V Total voltage max⁷58.8 V Total voltage max reset 58.1 V ²Duration longer than 1 second isconsidered for an overload ³Duration longer than 40 milliseconds isconsidered for an overload ⁴Time interval until next restart attempt⁵Maximum number of attempts in a row until definitive shutdown of BMS⁶When the highest cell voltage reach this value the charging is stoppedand cell balance will equalize the cell voltages. When the maximum cellvoltage falls bellow the value given by Cell voltage max reset thecharging is re-enabled ⁷When the battery voltage reach this level thecharging is stopped and again re-enabled when the voltage falls belowTotal voltage max reset value

Discharging

Discharging max current (<1 sec) (see note 2) 200 A Discharging maxcurrent (<40 msec) (see note 3) 250 A Discharge shutdown resting time(see note 4) 10 sec Shutdowns in a row (see note 5) 3 Cell voltage min⁸2.8 V Cell voltage min reset⁹ 3.7 V Discharge re-enable fuel gauge¹⁰ 10Ah ⁸If the lowest cell voltage reach this value the discharge is stopped⁹The lowest voltage amongst cell voltages must reach this value tore-enable discharging ¹⁰The minimum charged remaining capacity of thebattery, when the discharge is re-enabled

Cell Balancing

When cell balancing is started, the PWM is computed from the cellvoltage. The computing is done by adding the differences in cell voltagefrom the lowest cell voltage, together. After adding all cell voltages,the PWM value to each cell is computed to ensure total maximum powerdispassion don't exceed the limit

Cell balance max power¹¹ 27 W Cell balance start voltage average¹² 4.10V Cell balance peak start voltage¹³ 4.20 V Cell balance min chargecurrent¹⁴ 0.5 A ¹¹Maximum overall power dissipation allowed on the cellbalancing power resistors ¹²When the average voltage from all the cellsreaches this level and the Cell balance min charge current condition isfulfilled the cell balancing is triggered ¹³When the voltage of any ofthe cells reaches this value the cell balancing is triggered ¹⁴When thecharging current reaches this value and the Cell balance start voltageaverage condition is fulfilled the cell balancing is triggered

Temperature

Battery Temperature cut off high¹⁵ 70° C. Battery Temperature high reset60° C. Battery Temperature cut off low¹⁶ −20° C. Battery Temperature lowreset −10° C. BMS Temperature cut off high¹⁷ 100° C. BMS Temperaturehigh reset 90° C. ¹⁵When this battery temperature is reached thecharging and the discharging is stopped until the temperature fall toBattery Temperature high reset and then the functions are re-enabled¹⁶When this battery temperature is reached the charging and thedischarging is stopped until the temperature rise to Battery Temperaturelow reset and then the functions are re-enabled ¹⁷When this internal BMStemperature is reached the charging and the discharging is stopped untilthe temperature does not fall to BMS Temperature high reset and then thefunctions are re-enabled.

Fuel Gauge (Counting Amp/hours)

Fuel Gauge min input¹⁸ ±0.3 A Max value¹⁹ 105% of the specified capacitySelf learning²⁰ 1%/cycles ¹⁸The value of the charge/discharge currentmust exceed this value to be relevant for the gauge counting ¹⁹Maximumvalue indicated by a fuel gauge related to previously evaluated capacityusing self learning ²⁰When the battery is charged from empty to full thereal capacity can be reevaluated in the range of 1% from the previouslyobtained value in the self learning process

Sleep Mode

Enter sleep mode after (<300 mA) 60 sec Wakeup current 300 mA Standbysearch time 0.1 sec

Interfaces:

Single wire bus (communication with a charger or the diagnostic program)

1 Analogue output1 Open collector “High”/“Low” level output

BMS Internal (Cell) Communication Internal Communication

The master controls and monitors all the slaves by a communicationbetween slaves and master. The master handles the communication and theslaves only respond when asked. The communication is build upon a QSARTfull duplex, running on 5 kb with 9 bit transmission. When the 9th bitis set, the byte is a command, otherwise its data.

When receiving a package, it is stored in a buffer to calculate if thechecksum is the same as received. Only lithe checksum matches it willuse the package.

Start Byte/Address

In the beginning of all packages, there has to be a start bytecontaining the address of the slave witch is receiving or transmitting.It is possible to connect up to 120 slaves to the master. The slaveswill have there on address given in production for the master to accessthem. The addresses of the slaves will start from 1 and up to the numberof slaves connected.

List of Addresses: (9th Bit Set)

Value Address 0 Global address 1-120 Slave address

Command

The master sends packages to the slaves to give inform or giveinstructions. The command is always the first byte after the start byte.

There are always 3 command bytes in one package (Start byte, Command andChecksum)

List of Commands: (9th Bit Set)

Value Name Description  0-120 Start byte Start byte and address of theslaves 121 Send info to master Return data to master 122 Info frommaster Average battery voltage 123 Error check Check if one of theslaves has a error 124 Enter sleep-mode Put the slaves into sleep-mode125 Sync pulse The master will transmit a sync pulse 126 Calibration TheMaster transmit the real cell voltage and the slaves adjust the measuredvoltage 128-255 Checksum

Data

In some of the Packages it is necessary to transfer a few data bytes.When transmitting a data byte, the parity bit has to be low to indicate,it is a data byte and not a command. The receive buffer in the slaves isvery small and it is only packages is possible to transmit or receivepackages up to 16 bytes of data. When transmitting data values of 2bytes, LSB is sent first.

Checksum

The checksum is the last byte of the packages and data coming after whatis ignored only a new start byte in a new package is accepted. Since thecheck sum only calculate with 8 bits a value 25 is added for each paritybit. Every time the checksum has overflow the checksum is incrementedone time. The checksum it self is not added to the checksum and nottaken into calculation. The checksum can only have the value from 128 to255, if the value is out of range two different values is addeddepending of the checksum value.

Checksum Value to Add Parity 25 Each byte  1 Overflow  1  0-122 133(128 + 5) 123-127 10 128-255 No add

Ex1: Ex2: Ex3: Start byte: 15 Start byte: 120 Start byte: 15 Command:121 Command: 121 Command: 122 Data: No Data: No Data: 189 Data: No Data:No Data: 3 Checksum: 186 Checksum: 169 Checksum: 134Standard Master package:

Byte count Name 1 Start byte/Address 1 Command 2 Data (Cell BalanceVoltage) 2 Data (PWM Steps/Voltage) 1 Checksum 7 Total bytesStandard Slave package:

Byte count Name 1 Start byte/Address 1 Data (Status byte) 1 Data (PWMvalue) 2 Data (Battery Voltage) 1 Checksum 6 Total Bytes

Annex B

1 Master version 1.03.05

The master is controlling the BMS charger and discharge current andgatherings information from the slaves for cell balancing andprotection.

1.1 Measurements

The master measures charge current, discharge current, battery voltage,internal temperature and battery temperature. All measurements arecomputed 100 times/sec and average measurements are made each second.

1.2 Internal Communication

The master controls the communication between master and all slaves. Thefollowing flow chart is repeated all the time in normal operation.

1. The master is sending a synchronisation pulse for the slaves toadjust there clock frequency for drifting over temperature.

2. Information about cell balancing is send from the master to allslaves.

3. The master gathers voltage information from all the slaves.

1.3 Single Wire

Information about the status of the BMS and measured voltages of theslave is transmitted each second in normal operation.

Information from Master

Bytes Name Description 4 Status bytes Bit information 1 Cell countNumber of cells in the BMS 2 Battery voltage Measured battery voltage inthe BMS 2 Total battery voltage Slave voltages added together 2 Cellvoltage low The lowest cell voltage 2 Cell voltage average The averagecell voltage 2 Cell voltage high The highest cell volage 2 Fuel gaugeFuel gauge counter 2 Discharge current Discharge current 2 Chargecurrent Charge current 2 Temperature in Temperature inside BMS 2Temperature out Battery temperature 2 Cell voltage steps Total amount ofcell balancing 2 Cell voltage pwm Cell balance voltage for pwm

1.4 Power Supply

In normal operation the 5 volt and the 16 volt is power supply runningand stopped in sleep.

Flow chart when starting up the power supply:

1. Power up the 5 volt power supply and wait 80 msec

2. Measure offset on Op amps.

3. Power up AUX_START and wait 100 msec to charge the capacitors

4. Start PWM on driver and wait 100 msec

5. Stop AUX_START and power supply's are running.

The PWM for the 16 volt power supply is computed from the batteryvoltage and running with a fixed value to maintain an output voltage of16 volt. The PWM is adjusted each 10 msec.

1.5 Charging

The BMS is controlling the charging and protecting against overcharging. To control the charging the charge mosfet can be on/off and isonly on when charging is active. When connecting a charger and themaster detect the charger on CHARGER ACTIVE pin the mosfet is turn onand charging can begin. If the charge current is below 0.5 A for 30 seccharging is stopped and the charger has to be disconnected before it isre-enabled. If the charge current is above limit charging is stopped andwill retry 3 times before locking. To unlock, remove wakeup signal andcharger for 10 sec.

If battery temperature exceeds limit, charging is stopped until thetemperature is 10° C. within limits, when automatically restarted.

If the BMS temperature exceeds limit, charging is stopped until thetemperature is 10° C. within limits, when automatically restarted.

1.6 Discharging

The BMS is controlling discharging and protecting against deep dischargeby switching off the discharge mosfet. If one or more cells aredischarged, the discharge mosfet is switched of and the master will gointo sleep. Discharge is only active if wakeup signal is active and themaster will wakeup and power up the control circuits, but only if thecell voltages are within limits discharge is activated. Otherwise themaster will go back into sleep again after 30 sec.

If the discharge current is above limit discharging is stopped and willretry 3 times before locking. To unlock, remove wakeup signal andcharger for 10 sec.

If battery temperature exceeds limit, discharging is stopped until thetemperature is 10° C. within limits, when automatically restarted.

If the BMS temperature exceeds limit, discharging is stopped until thetemperature is 10° C. within limits, when automatically restarted.

1.7 Fuel Gauge

The fuel gauge is counting all currents going in and out of the battery.If the measured current value is below 0.3 A it is not counted into thefuel gauge. The fuel gauge value is not allowed to go below zero orabove 105% of specified capacity.

1.8 Sleep

If wakeup signal and charger has been missing for 30 sec the BMS will gointo sleep to minimize power consumption. The master wakeups when wakeupsignal or charger is connected. If there is under voltage on one or moreslaves, the master will only power up the control circuits and check theslave voltages and go back into sleep. To wakeup the master once more,first remove wakeup signal and reconnect.

1.9 Software Settings Power Supply Settings

Description Value Power supply start up voltage 25.55 V Power supplyoutput voltage 23 V Power Supply Max PWM Pulse 90%

Current Settings

Description Value Charge current max slow 35 A Charge current max slowtime 1 sec Charge current max fast 50 A Charge current min 0.5 ADischarge current max slow 150 A Discharge current max slow time 8 secDischarge current max fast 250 A Fuel gauge min detection 0.3 A Fuelgauge charge efficiency 100% Battery capacity 80 Ah

Voltage Settings

Description Value Cell voltage min 2.8 V Cell voltage min reset 3.3 VCell voltage max 4.1 V Cell voltage max reset 4.0 V Cell balance startvoltage (single cell) 4.0 V Cell balance start voltage (average) 3.8 VCell balance total power dispassion. 27 W

Temperature Settings

Description Value BMS internal temperature max 105° C. BMS internaltemperature reset 90° C. Battery charging temperature min −10° C.Battery charging temperature min reset 0° C. Battery chargingtemperature max 50° C. Battery charging temperature max reset 40° C.Battery discharging temperature min −20° C. Battery dischargingtemperature min reset −10° C. Battery discharging temperature max 70° C.Battery discharging temperature max reset 60° C.

2 Slave Version 1.03.01

The Slave is measuring the voltage of the cell and controlling the cellbalance with information from the master.

2.1 Measurements

The slave measures the cell voltage each 9.5 ms and compute an averagevalue after 50 measurements. The cell balancing is stopped whilemeasuring to avoid wrong value caused by voltage drop in cables. Themeasurement is transmitted to the master. The measurement is calibratedin production via communication.

2.2 Cell Balance

The slave is making the cell balancing controlled values received fromthe master. The slave receives a voltage from the master, the differencebetween this value and measured value are multiplied and put in second.A fixed computed value is also received from the master and multipliedwith the delta voltage used to compute the duty cycle for the cellbalance PWM. If the cell voltage is lower than the received voltage frothe master the PWM is set to zero.

2.3 Communication

The slaves each the there own address for the master to recognize themand control the battery. The slave receive synchronise pulse and valuesfor cell balance each second and the master gets voltage measurement andstatus information each second.

2.4 Sleep

If the communication from the master stops for more than 10 sec theslave is put into sleep and waiting for communication to start again.

3 Internal Communication

The master controls and monitors all the slaves by a communicationbetween slaves and master. The master handles the communication and theslaves only respond when asked. The communication is build upon a QSARTfull duplex, running on 5 kb with 9 bit transmission. When the 9th bitis set, the byte is a command, otherwise its data.

When receiving a package, it is stored in a buffer to calculate if thechecksum is the same as received. Only if the checksum matches it willuse the package.

3.1 Start Byte/Address

In the beginning of all packages, there has to be a start bytecontaining the address of the slave Witch is receiving or transmitting.It is possible to connect up to 120 slaves to the master. The slaveswill have there on address given in production for the master to accessthem. The addresses of the slaves will start from 1 and up to the numberof slaves connected.

List of Addresses: (9th Bit Set)

Value Address 0 Global address 1-120 Slave address

3.2 Command

The master sends packages to the slaves to give inform or giveinstructions. The command is always the first byte after the start byte.

There are always 3 commando bytes in one package (Start byte, Commandand Checksum)

List of Commands: (9th Bit Set)

Value Name Description  0-120 Start byte Start byte and address of theslaves 121 Send info to master Return data to master 122 Info frommaster Average battery voltage 123 Error check Check if one of theslaves has a error 124 Enter sleep-mode Put the slaves into sleep-mode125 Sync pulse The master will transmit a sync pulse 126 Calibration TheMaster transmit the real cell voltage and the slaves adjust the measuredvoltage 128-255 Checksum

3.3 Data

In some of the Packages it is necessary to transfer a few data bytes.When transmitting a data byte, the parity bit has to be low to indicate,it is a data byte and not a command. The receive buffer in the slaves isvery small and it is only packages is possible to transmit or receivepackages up to 16 bytes of data. When transmitting data values of 2bytes, LSB is sent first.

3.4 Checksum

The checksum is the last byte of the packages and data coming after whatis ignored only a new start byte in a new package is accepted. Since thecheck sum only calculate with 8 bits a value 25 is added for each paritybit. Every time the checksum has overflow the checksum is incrementedone time. The checksum it self is not added to the checksum and nottaken into calculation. The checksum can only have the value from 128 to255, if the value is out of range two different values is addeddepending of the checksum value.

Checksum Value to Add Parity 25 Each byte  1 Overflow  1  0-122 133(128 + 5) 123-127 10 128-255 No add

Ex1: Ex2: Ex3: Start byte: 15 Start byte: 120 Start byte: 15 Command:121 Command: 121 Command: 122 Data: No Data: No Data: 189 Data: No Data:No Data: 3 Checksum: 186 Checksum: 169 Checksum: 134

Standard Master Package:

Byte count Name 1 Start byte/Address 1 Command 2 Data (Cell BalanceVoltage) 2 Data (PWM Steps/Voltage) 1 Checksum 7 Total bytes

Standard Slave Package:

Byte count Name 1 Start byte/Address 1 Data (Status byte) 1 Data (PWMvalue) 2 Data (Battery Voltage) 1 Checksum 6 Total Bytes

1. A modular battery management system for controlling and monitoring aplurality of battery cells connected in series in a battery connected toa load, the modular battery management system comprising: a plurality ofbattery monitoring modules, each of the battery monitoring modulesincluding a cell balancing circuit, a slave sensing circuit, and atleast one temperature sensor operable to monitor the temperature of abattery cell to determine when a first excessive temperature has beenreached in said battery cell during operation of said battery cell; acentral controlling microcontroller operatively connected to each of theplurality of battery monitoring modules and configured for controllingeach of the plurality of battery monitoring modules, thereby to controlthe charging of each of said plurality of battery cells; each of thebattery monitoring modules being operatively connected to one or more ofsaid plurality of battery cells such that each individual battery cellof the plurality of battery cells has an electric connection to one ofthe plurality of battery monitoring modules, whereby each of theplurality of battery monitoring modules is operable to: measure acharging state of a respective battery cell during the charging of therespective battery cell; and before a maximum charging state is reachedin the respective battery cell, establish a shunt across the respectivebattery cell, thereby allowing a continued charging of remaining batterycells in the plurality of battery cells.
 2. The modular batterymanagement system of claim 1, wherein each of the plurality of batterymonitoring modules is operable to shut down charging of the respectivebattery cell when the first excessive temperature of said respectivebattery cell is reached.
 3. The modular battery management system ofclaim 1, wherein each of the plurality of battery monitoring modules isoperable, when the shunt is established, to communicate to the centralcontrolling microcontroller that the maximum charging state has beenreached in the respective battery cell in which the maximum chargingstate has been reached.
 4. The modular battery management system ofclaim 1, wherein each of the battery monitoring modules includes atleast a second temperature sensor operable to monitor the temperature ofsaid cell balancing circuit and said slave sensing circuit to determinewhen a second excessive temperature has been reached during operation ofsaid cell balancing circuit and said slave sensing circuit, wherein eachof the plurality of battery monitoring modules is operable to shut downwhen the second excessive temperature is reached.
 5. The modular batterymanagement system of claim 1, wherein each of the plurality of batterymonitoring modules is operable, during discharging of the battery, toinform the central controlling microcontroller when a non-zero minimumvoltage has been reached in the respective battery cell so as to causethe central controlling microcontroller to disconnect all the cells inthe plurality of battery cells from the load in order to prevent furtherdischarging of the respective battery cell in which the non-zero minimumvoltage has been reached to a cell-ruining voltage below the non-zerominimum voltage.
 6. The modular battery management system of claim 1,wherein the central controlling microcontroller is operatively connectedto each of the plurality of battery monitoring modules via a common databus.
 7. The modular battery management system of claim 1, wherein thecentral controlling microcontroller is operatively connected to each ofthe plurality of battery monitoring modules via a wireless connection.8. The modular battery management system of claim 1, wherein said cellbalancing circuit is configured to establish the shunt in response to asignal from said slave sensing circuit when the respective slave sensingcircuit has measured a maximum voltage across the respective batterycell that has reached the maximum charging state.